1. Field of the Invention
The present invention relates to a toroidal type continuously variable transmission to be used for automobiles or various industrial machines.
2. Related Background Art
A toroidal type continuously variable transmission, as shown in FIGS. 14 and 15 has been studied for use in an automobile. This toroidal type continuously variable transmission has, as disclosed in, e.g., Japanese Utility Model Laid-Open Application No. 62-71465, an input shaft 1 and an output shaft 3. An input-side disk 2 is provided concentrically with the input shaft 1. An output-side disk 4 is fixed to an end portion of the output shaft 3. The inner surface of a casing containing the toroidal type continuously variable transmission or a supporting bracket mounted in the casing is provided with trunnions 6, 6 to be swung around axes 5, 5 located in diagonal positions with respect to the input and output shafts 1 and 3.
The trunnions 6, 6 are provided on outer surfaces of both end portions with the axes 5, 5. The center portions of the trunnions 6, 6 support the base portions of respective displacement axes (shafts) 7, 7. The inclinations of the displacement axes 7, 7 can be freely adjusted by swinging the respective trunnions 6, 6 around the axes 5, 5. Power rollers 8, 8 are supported rotatably around the displacement axes 7, 7 supported by the trunnions 6, 6. The power rollers 8, 8 are held tightly between the input-side and output-side disks 2 and 4.
Inner side surfaces 2a and 4a of the input-side and output-side disks 2 and 4 which oppose each other, have circular arc shapes in cross section with the axes 5, 5 as the centers. Spherically formed peripheral surfaces 8a, 8a of the power rollers 8, 8 are in contact with the inner side surfaces 2a and 4a.
A loading cam type pressing device 9 is provided between the input shaft 1 and the input-side disk 2. The input-side disk 2 is pressed elastically toward the output-side disk 4 by the pressing device 9. The pressing device 9 is constituted of a cam plate 10 that rotates together with the input shaft 1 and a plurality of rollers 12, 12 (e.g., four rollers) held by a retainer 11. One side surface of the cam plate 10 (left side surface in FIGS. 14 and 15) forms a cam surface 13 having irregularities in the circumferential direction. Also, an outer side surface of the input-side disk 2 (the right-side surface in FIGS. 14 and 15) forms a cam surface 14. The plurality of rollers 12, 12 are supported rotatably around axes in the radial directions with respect to the center of the input shaft 1.
In the above-structured toroidal type continuously variable transmission, when the cam plate 10 is rotated in accordance with rotation of the input shaft 1, the plurality of rollers 12, 12 are pressed by the cam surface 13 against the cam surface 14 of the input-side disk 2. As a result, as soon as the input-side disk 2 is pressed against the power rollers 8, 8 the input-side disk 2 is rotated due to the engagement of the cam surfaces 13, 14 and the plurality of rollers 12, 12. Then, the rotation of the input-side disk 2 is transmitted via the power rollers 8, 8 to the output-side disk 4, whereby the output shaft 3 fixed to the output-side disk 4 is rotated.
When changing the rotation speed between the input shaft 1 and the output shaft 3 by performing deceleration between the input shaft 1 and the output shaft 3, the trunnions 6, 6 are swung around the axes 5, 5 to incline the displacement axes 7, 7 such that the peripheral surfaces 8a, 8a of the power rollers 8, 8 are brought into contact with portions of the inner side surface 2a of the input-side disk 2 close to the center thereof and portions of the inner side surface 4a of the output-side disk 4 close to the outer periphery thereof, as shown in FIG. 14.
When performing acceleration, the trunnions 6, 6 are swung to incline the displacement axes 7, 7 such that the peripheral surfaces 8a, 8a of the power rollers 8, 8 are brought into contact with portions of the inner side surface 2a of the input-side disk 2 close to outer periphery thereof and into contact with portions of the inner side surface 4a of the output-side disk 4 close to the center thereof, as shown in FIG. 15. When the inclinations of the displacement axes 7, 7 are set so as to be between the positions shown in FIGS. 14 and 15, it is possible to obtain an intermediate speed ratio between the input shaft 1 and the output shaft 3.
Further, FIG. 16 shows a more detailed toroidal type continuously variable transmission for an automobile as disclosed in Japanese Utility Model Laid-Open Application No. 62-199557. The rotation of an engine is transmitted via a clutch 15 to an input shaft 16 to rotate the cam plate 10 connected to the intermediate portion of the input shaft 16 by the spline joint. Due to the operation of the pressing device 9, which includes the cam plate 10, the input-side disk 2 is rotated while being pressed toward the output-side disk 4 (the leftward direction in FIG. 16). The rotation of the input-side disk 2 is transmitted to the output-side disk 4 via the power rollers 8, 8.
The output-side disk 4 is supported by a needle bearing 17 around the input shaft 16. A cylindrical output shaft 18 formed integrally with the output-side disk 4 is supported by an angular type ball bearing 20 in a housing 19. One end of the input shaft 16 (right end in FIG. 16) is supported rotatably by a roller bearing 21 in the housing 19 and the other end thereof is supported rotatably via a sleeve 23, by an angular type ball bearing 22 in the housing 19.
A transmission gear 26 has a forward drive gear 24 and a rearward drive gear 25 formed integrally with the forward drive gear 24 and is connected to the outer peripheral surface of the output shaft 18 by the spline joint. When driving the automobile forward, the transmission gear 26 is moved rightward to engage the forward drive gear 24 directly with a forward drive coupling gear 28 provided on the intermediate portion of a take-out shaft 27. When driving the automobile rearward, the transmission gear 26 is moved leftward to engage the rearward drive gear 25 with a rearward drive coupling gear 29 fixed to the intermediate portion of the take-out shaft 27 via an intermediate gear (not shown).
In the above-structured toroidal type continuously variable transmission, when the input shaft 16 is rotated via the clutch 15 by the engine and the transmission gear 26 is shifted in a proper direction, it is possible to rotate the take-out shaft 27 in a desired direction. Also, when the trunnions 6, 6 are swung to change contact positions of the peripheral surfaces 8a, 8a of the power rollers 8, 8 and the inner side surfaces 2a, 4a of the respective input-side and output-side disks 2, 4, it is possible to change the rotation speed ratio of the take out shaft 27 to the input shaft 16.
During driving of the above-structured toroidal type continuously variable transmission, the input-side disk 2 is pressed toward the output-side disk 4 in accordance with the operation of the pressing device 9. As a result, a thrust load in the rightward direction in FIG. 16 is applied to the input shaft 16 supporting a cam plate 10 constituting the pressing device 9 as a force reactive to above pressure. This thrust load is supported by the ball bearing 22 via a nut 30 fastened on the end portion of the input shaft 16 and the sleeve 23. Also, due to the operation of the pressing device 9, a thrust load in the leftward direction in FIG. 16 is applied to the output shaft 18 via the input-side and output-side disks 2, 4 and the power rollers 8, 8. This thrust load is supported by the ball bearing 20 via a stop ring 33 fitted on the output shaft 18.
In FIG. 16, reference numerals 31 and 32 designate a clutch for an engine brake and a clutch for direct connection, respectively. The structures and operations of these are disclosed in detail in Japanese Utility Model Laid-Open Application No. 62-199557 and are irrelevant to the point of the present invention, so the detailed description thereof is omitted.
Further, during driving of the above toroidal type continuously variable transmission, in addition to the thrust loads applied to the input and output shafts 16 and 18, thrust loads are applied to the power rollers 8, 8. Therefore, thrust rolling bearings 34, 34 are provided between the power rollers 8, 8 and the respective trunnions 6, 6 to support the thrust loads applied to the respective power rollers 8, 8.
each of the thrust rolling bearings 34, 34 has a plurality of rolling elements 35, 35, a retainer 36 for holding the rolling elements 35, 35 rotatably and an outer race 37. The plurality of rolling elements 35, 35 are formed of bearing steel or ceramic in the shape of a ball or a taper roller. These rolling elements 35, 35 are in contact with a raceway surface formed on the outer end surface of each power roller 8, 8 and a raceway surface formed on one side surface of each outer race 37, 37. The retainer 36 is formed of metal 6r plastics like a disk and holds the rolling elements 35, 35 rotatably in pockets 38, 38, one per pocket. The pockets 38, 38 are formed in the retainer 36 in an intermediate portion in the radial direction at regular intervals in the circumferential direction. The outer races 37, 37 are formed of bearing metal or ceramic in the shape of a disk and are brought into contact with the inner side surfaces of the respective trunnions 6, 6 via spacers 39, 39 (refer to FIG. 17) formed in the shape of a disk too.
During driving of the toroidal type continuously variable transmission, the thrust rolling bearings 34, 34 rotate at high speed while supporting thrust loads applied to the power rollers 8, 8. Therefore, during that time, it is necessary to supply a sufficient amount of lubricating oil to the thrust rolling bearings 34, 34.
Therefore, as shown in FIG. 17, one or a plurality of oiling holes 40, 40 are formed in the outer race 37 and lubricating oil is supplied through the oiling holes 40, 40 forcibly. The lubricating oil supplied forcibly through the oiling holes 40, 40 flows through the space between the inner surface of the outer race 37 and the outer surface of the retainer 36 and the space between the inner surface of the retainer 36 and the outer end surface of the power roller 8 to lubricate rolling portions of the rolling elements 35, 35.
When supplying lubricating oil to the above-structured thrust rolling bearings 34, 34, it is conceivable that the supply of lubricating oil could become partially deficient. That is, as shown in FIG. 18A, when the retainer 36 is located midway between the inner surface of the outer race 37 and the outer end surface of the power roller 8, the lubricating oil flows through both the space between the inner surface of the outer race 37 and the outer surface of the retainer 36 and the space between the inner surface of the retainer 36 and the outer end surface of the power roller 8, causing no problem.
However, when the lubricating oil is poured through the oiling holes 40, 40 formed in the outer race 37 toward the outer surface of the retainer 36, the retainer 36 is pressed by the flow of the lubricating oil and is liable to be displaced toward the power roller 8, as shown in FIG. 18B. When the inner surface of the retainer 36 is brought into contact with the outer end surface of the power roller 8 owing to such displacement, a sufficient amount of lubricating oil cannot be applied to contact portions of the raceway surface formed on this outer end surface and rolling contact surfaces of the rolling elements 35.
As a result, abrasion loss becomes large at the Contact portions of the raceway surface of the outer end surface of the power roller 8 and the rolling contact surfaces of the rolling elements 35. Also, in an extreme case, the contact portions might be burned.